1.Use the transform properties window invoked with N key to accurately place objects in object mode or verticese, edges and faces in editmode.
That pink dot is your objects center. You can change this via the buttons on the mesh tab in the edit buttons (F9). This only works in objectmode.
You can aloso cause objects or subsets of meshes to transform or scale around the 3D cursor. Default is transforms around the object’s center, but you can toggle the function 2 buttons to the left of the little hand icon in the 3D viewport or with the “period” hotkey. “comma” hotkey will toggle back to object centers.
Edit: Holding down “Ctrl” key while transforming or scaling objects or mesh subsets will cause them to snap to the grid or parts in between the gridlines if they are not already alligned to the grid.